Thin-walled stackable shallow containers such as dishes, plates and the like

ABSTRACT

A stackable shallow container such as a plate is integrally formed of thermoplastic sheet material with a continuous closed outline figure stacking fin consisting of tightly folded together adjacent continuous wall regions depending axially from the bottom wall, side wall or rim of the container. One method and apparatus for forming such a container from sheet material comprises relatively axially movable concentric tool parts spaced radially the thickness of the sheet material for folding the container wall to provide the fin.

United States Patent 1191 Thiel [4 Oct. 7, 1975 [54] THlN-WALLED STACKABLE SHALLOW 3,155,303 11/1964 Fenkel 229/25 CONTAINERS SUCH AS DISHES, PLATES 11951770 7/1965 9 AND THE LIKE 3,442,420 5/1969 Edwards 206/520 [76] Inventor: Alfons Wilhelm Thiel, Uferstrasse FOREIGN PATENTS OR APPLICATIONS 15, D 6500 M i Germany 572,755 11/1958 Belgium 206/520 22 Filed: Apr. 30, 1973 [30] Foreign Application Priority Data Sept 6, 1972 Germany 7232864- Jan, 11, 1973 Germany 2301215 [52] US. Cl. 206/520 [51] Int. Cl B65d 21/02 [58] Field of Search 229/25; 220/23.6; 206/515, 519, 520

[56] References Cited UNITED STATES PATENTS 2,607,284 8/1952 Fowler 206/520 X 2,932,437 4/1960 Wilcox 206/515 X Appl. No.1 355,503

Primary Examiner-Edward J. McCarthy Attorney, Agent, or FirmStrauch, Nolan, Neale, Nies & Kurz [57] ABSTRACT A stackable shallow container such as a plate is integrally formed of thermoplastic sheet material with a continuous closed outline figure stacking fin consisting of tightly folded together adjacent continuous wall regions depending axially from the bottom wall, side wall or rim of the container. One method and apparatus for forming such a container from sheet material comprises relatively axially movable concentric tool parts spaced radially the thickness of the sheet material for folding the container wall to provide the fin.

10 Claims, 9 Drawing Figures US. Patent Oct. 7,1975 Sheet 2 of4 3,910,415

Fig. 4

US. Patent Oct. 7,1975 Sheet 3 01 4 3,910,415

US. Patent Oct. 7,1975 Sheet 4 of4 3,910,415

Fig.9

THIN-WALLED STACKABLE SHALLOW CONTAINERS SUCH AS DISHES, PLATES AND THE LIKE The invention relates to shallow containers such as dishes, plates and the like whereof the diameter of the bottom wall is greater than the container depth, and made in one-piece from thermoplastic sheet material, and methods and apparatus for manufacturing the same.

in its preferred embodiments the container of the invention comprises a generally planar transverse bottom wall which may be corrugated, an inclinedperipheral side wall essentially conically widening in the direction away from the bottom wall, an outer rim around the periphery of the side wall, and a stacking fin extending in an axial direction from the container, preferably in the form of an axial fold of the container material that is essentially twice as thick as the container wall and preferably located in an area of the container wall which is normal to the container axis. The fin may be in the bottom wall, the side wall or the rim. Essentially the stacking fin is a fold formed solely by two closely pressed wings of the same length integrally joined at the lower seating edge of the fin. These wings radially abut in full surface engagement so that at the upper end of the fin within the container there will be substantially no groove which might be penetrated by the fin above or into which food or other particles may undesirably enter.

BACKGROUND AND SUMMARY OF INVENTION Stackable shallow containers are known that are integrally formed of thermoplastic material and have bottom walls, upwardly and outwardly inclined side walls and peripheral rims around the upper edges of the side walls. Stacking projections formed in the container walls have been proposed for such containers, but these have been relatively wide beads having a thickness several times that of the container wall and they provide correspondingly wide open grooves at the opposite side of the container wall. In stacking the beads of the upper containers at least partly penetrate the open grooves of the containers below to reduce the stacking space required. This construction is not desirable for shallow containers such as plates and dishes which become wedged together and difficult to separate later. Also particulate material may undesirably enter the open grooves.

Attempts have been made to remedy this drawback by providing the stacking beading and the inevitable associated groove with wavy or other special shapes, or by mounting the stacking beading with different radii in different sections and at different spacings from the container axis (German Gebrauchsmuster Nos. 7,047,845, 7,125,640). This strongly reduces the probability of wedging on the part of beading and groove, but does not entirely eliminate it. in such arrangements, where bead and groove sections will fit, they stack closer together than where they do not fit, and this causes oblique stacking and wedging of the stacked containers.

The major object of the invention is to provide shallow containers such as plates, dishes and the like provided with a stacking arrangement that can be easily and reliably manufactured, incorporating axial stacking fins and avoiding the drawbacks of the foregoing proposals. A more specific object of the invention is to provide a thin-walled, stackable one-piece container, which is manufactured by thermal forming of thermoplastic sheet material, and which includes a bottom wall, a side wall extending from the bottom and essentially widening in conical shape towards the open container side, and an outer rim around the peripheral wall at the open side, with a stacking fin of uniform height extending axially of the container and preferably shaped as a tight axial fold, essentially only twice the thickness of the container wall and located in a region of the wall that is as nearly as possible in a plane normal to the container axis- A further object of the invention is to provide a novel shallow container structure wherein at least one stacking fin axially depends from either the bottom wall, the side wall or the rim of the container, such a fin comprising closely engaged reversely folded adjacent portions of the container wall and extending in a continuous closed figurepath, the lower seating edge of the tin being a rounded fold region between those portions and the upper edges of those portions which lie in the container wall being so closely engaged as to prevent penetration of the fin of the next uppermost container of the stack and prevent the accumulation of undesirable material within the fold.

Where the container is subdivided into compartments, a number of depending fins usually of the same height corresponding to the number of compartments may be formed in the bottom wall, the lower edges of all of the fins lying in a common plane, and it is another object of the invention to provide such container structure.

A further object of the invention is to provide in a shallow container wherein the stacking fin is formed in the conical side wall structure an annular ledge that is normal to the container axis and wherein the container wall may be folded to provide an axially directed folded fin structure.

Another major object of the invention is to provide a novel method of making one-piece Stackable shallow containers such as plates and dishes from sheet thermoplastic material characterized by thermally forming the container in the sheet material with a recess of predetermined depth in the region that is to provide a stacking fin, and then back-forming the container at that region to achieve the final container wall shape and at the same time form in that region a tight wall fold of predetermined height constituting the depending stacking fin. Further to this object, the tight fold at the fin may be achieved by mutually laterally compressing the side wall portions of the fold at the end of the back-forming operation.

It is still a further object of the invention to provide apparatus for carrying out the foregoing method in a continuous operation wherein a novel thermal forming tool arrangement comprises relatively movable tool parts that define between them an annular fold shaping space that is about twice the thickness of the thermoplastic sheet material. More specifically as to this object the tool parts are respectively an annular fixed outer part and an axially movable inner part with the annular fold forming space disposed laterally between them. A still further specific related object is to provide in or on the tool parts an arrangement for laterally compressing the sides of the fold into intimate full surface engagement.

A further specific object of the invention is to provide a tool structure in which the lateral surfaces of the shaping groove are arrayed essentially parallel to each other and at an acute angle outwards with respect to the forming axis to automatically cause a surface pressure at both sides of the stacking fold at the end of the back-shaping operation.

It is also an object of the invention to provide the foregoing apparatus with an ejection device for the formed articles, and with an automatic control for the operational sequences, the forming tool parts and the ejection device being so controlled that ejection will only occur after the forming tool parts have been returned from their back-shaping position to their initial blocking position.

Further objects, characteristics and advantages of the invention will be found in the description below of several embodiments illustrated by the drawing- BRIEF DESCRIPTION OF DRAWINGS FIG. I is a partial sectional view showing stacked formed plates according to one'embodimcnt of the invention; I

FIG. 2 is similar partial section showing stacked plates according to a further embodiment;

FIG. 3 is a similar partial section, showing stacked plates according to a still further embodiment;

FIG. 4 is a bottom plan view showing a formed plate corresponding to the FIG. I embodiment;

FIGS. 5 and 6 are bottom plan views showing com partmented formed plates having different types. of de pending stacking fins;

FIG. 7 is a diagrammatic view illustrating an apparatus and method for carrying out the invention in automatic production; and

FIGS. 8 and 9 are partial sections showing successive plate forming operations in the thermo-forming equipment station of FIG. 7.

PREFERRED. EMBODIMENTS FIG. 1 illustrates two stacked plates Leach having an outer upwardly convex peripheral rim 2, an inclined flat preferably conical side wall structure 4 and a corru gated bottom wall .6. These plates are preferably each one-piece articles formed by deep drawing from uniform thickness synthetic thermoplastic sheet material that will hold a given shape after forming. In this embodiment corrugation of wall 6 provides resistance to deformation under pressure. These plates are disposable after a single use.

' In the FIG. I embodiment an integral constant depth relatively stiff continuous stacking fin 5 is provided extending circularly around and projecting downwardly from the outer periphery of bottom wall 6 adjacent the loweredge of side wall 4. Fin 5 consists of side Wings 511 and 512 formed by reverse bends of adjacent annular regions of the plate material. The wings are intimately pressed into full surface abutment around their adjacent peripheral surfaces, so that the radial thickness of fin 5 is twice the thickness of the plate material. At

their lower ends the wings are integrally joined and the juncture of the wings within the bottom of the formed plate is a substantially sealed line. In the drawings the Wings 511 and 5b are exaggeratedly shown as slightly separated for clarity of disclosure.

In a stack of these plates. the smooth rounded lower edge of the fin 5 of the upper plate will seat in the flat bottom wall as shown, the only contact between the successive superposed plates being the rounded lower edge of the 'upper plate stacking fold resting on the closed upper edge of the stacking fold of the lower plate.

FIG. 2 illustrates two stacked plates, each having an outer flat peripheral rim 12 terminating in a down wardly inclined ledge, an inclined flat preferably conical side wall structure 14 and a flat bottom wall 13 parallel to rim '12; In this embodimentthe downwardly projecting integral constant depth stacking fold 15 is formed in the rim by reversely bent wings 15a and 15b that are preferably intimately associated as described above for wings 5a and 5b of fin 5.

FIG. 3 illustrates two stacked plates. each having an upwardly convex outer rim 22, a flat bottom wall 23 I and an inclined flat preferably conical side: wall structure 24. In this embodiment the side wall structure in- I eludes an annular intermediate ledge portion 26 that ,is

preferably parallel to bottom wall 23 and is formed with the depending annular constant depth stacking fin by reverse bending of wings 25a and 25b of the plate material at approximately the center of the ledge. This.

of the stack have contact only between the rounded lower edge of the upperplate stacking fold and the closed upper endof the stacking fold within the lower plate.

FIG. 4 is a bottom plan viewofa plate I of FIG 1 and its shows the circular stacking fin 5 as a circular ring provided in the outer flat smooth annular portion 3a of the bottom wall surrounding the corrugated or similarly reenforced central portion.

FIG. 5 shows in a bottom planview a plate 31 in which the side wall 4 and outer rim 2 are as in FIG. 4, but wherein the bottom of the plate is formed with a separation rib 32 that projects up into the interior of the plate to divide that interior into separate compartments as for separate foods. Rib 32 also provides deformation resistance for the plate. Here the plate bottom 33 comprises a central corrugated or similarly reenforced central portion 33b surrounded by a flat annular smooth portion 33a. Also, instead of a single depending continuous stacking fin, two stacking fins 35a and 35b are formed in the bottom wall, one below each plate compartment. As shown the fins 35a and 35b each have a circular outer periphery adjacent the juncture of the central bottom wall with annular portion 330 and an inner periphery lying along and adjacentthe dividing rib 32.

' FIG. 6 shows in a bottom plan view a plate 41 having an outer rim 2 and an inclined conical side wall 4 as in FIGS. 4'and 5. Here the interior of the plate is separated into three compartments by the upstanding T- shaped rib arrangement shown at 42a, 42b. Like rib 32 in FIG. 5, this T-shaped rib reenforced the plate bot tom. In this embodiment three continuous circular depending stacking fins are provided in the corrugated bottom wall 431;. one below each compartment. These fins are shown at 45a, 45b and 45c. and preferably their centers are'on a common circle having a common center with the plate. While these three stacking folds are shown of the same diameter they may be of different diameters oreven different shapes or contours.

Where more than one fin is formed in the bottom as in FIGS. 5 and 6, the lower seating edges of the fins lie in a common plane normal to the container axis.

The foregoing embodiments of FIGS. l6 illustrate several various modes of providing stacking folds on the plate bottoms, but the invention is not limited to these particular shapes and arrangements. The divided compartment structures of FIGS. 5 and 6 could be used in the embodiments of FIGS. 2 and 3.

FIG. 7 diagrammatically illustrates an apparatus and method for automatic production of the plates of FIGS. 1,6.

A web 61 of thermoplastic sheet material is drawn from a rotatable reel mounted supply roll 62 by an endless belt feed conveyor 63 and is heated to plastic condition for shaping by a heater 64 disposed above the conveyor. Conveyor 63 is intermittently driven to advance selected lengths of the web in steps in timed sequence. Each heat softened length of the leading end of the web is fed into and periodically stopped in the thermo-shaping equipment 65.

In some apparatus and processes, the web may proceed in relatively soft condition directly from an extruder to the equipment at 65, but in either case successive lengths of thermally softened web material are disposed for a predetermined period in the forming equipment 65.

In the arrangement of FIG. 7, the thermo-shaping equipment comprises a thermo-shaping tool 51 having a stationary outer circular tool part 52 and an axially movable inner tool part 53 that may be selectively displaced up or down during the forming operation by a fluid pressure cylinder 66 which may be hydraulic or pneumatic. A counter tool 67 is selectively displaced by a pneumatic or hydraulic cylinder 68 between the illustrated lower. closed position where it forms arrested softened section of the web against the stationary tool part 52 and the arrested movable tool part 53, and an open upper position above the pathof the web.

In the thermo-shaping tool 51 the upper tool part 67 may be solid and shaped on its lower surface to the desired contour for forming the softened web to the preliminary form illustrated in the tool at FIG. 7, or the upper tool part may be of the pneumatic type wherein the part 68 may be a source of air under pressure adapted to deliver pressurized air into the closed space above the web and force the heat softened plastic into the preliminary shape illustrated in FIG. 7. In the invention it is not critical which mode of forming is employed to attain this preliminary step.

Ejector rods 69 slidable in the stationary tool part are connected by a common bridge to a pneumatic or hydraulic cylinder 70 which may selectively dispose the rods in inactive position as shown or displace them upwardly to eject a formed section of the web as will appear. For some shallow plate formation these ejectors may be omitted as unnecessary.

A central control apparatus 71 is provided for selectively supplying fluid under pressure tocylinders 66, 68 and 70 in the desired sequence for the forming operations. The control apparatus 71 is so designed that cylinder 70 may be actuated to displace the ejector rods upwardly only the movable tool 53 has been moved by cylinder 66 to its lowermost position shown in FIG. 7 and when counter tool 67 has been raised by cylinder 68 in its upper open position.

The length of web 61 standing in the thermo-forming equipment 65 is shaped to the required plate contour at 72 and, while still remaining as part of the web, is moved out of the thermo-forming equipment to the cutting station 73. The structure and operation of the thermo-forming equipment will be further described in connection with FIGS. 8 and 9.

At station 73 the formed plates 72 are cut out of the web, separated from the web and piled in a stack. A punch mechanism in the station comprises a stationary annular punch die receptacle 74 and a movable annular cutting and punching die member 75 adapted to be selectively displaced between an upper inactive position and a lower cutting position by a pneumatic or hydraulic cylinder 76 also operatively connected to be intermittently actuated in timed sequence and in synchronism with equipment 65 by control apparatus 71.

As each formed plate 72 is cut out of the web it drops through the punch receptacle to accumulate in a stack forming device 77 below the punch. An intermittently moved conveyor for moving stacks of a selected number plates away from beneath the punch may be used at 77.

While a vertically acting punch die is shown at 73, a horizontally acting structure with suitable devices for catching and stacking the severed formed plates may be provided.

Referring to FIGS. 8 and 9 that disclose a die assembly wherein a plate of the type shown in FIG. I is formed, the movable tool part 53 is shown in FIG. 8 in its lowermost position which is the position that it is held by cylinder 66 while the length 61 of the thermoplastic sheet material is being preliminarily formed and shaped to the intermediate condition shown in FIG. 8. The depth d of cylindrical recess 56 in the bottom of the plate is twice the depth of the stacking fold 5 to be formed in the next operation shown in FIG. 9.

As shown in FIG. 8, a heat insulating annular insert 57 of synthetic rubber of the like may be provided between the fixed tool part 52 and the movable tool part 53 during the forming operation resulting in the plate of FIG. 8, for the purpose of preventing undue drain of heat and undesirable cooling ofthe portion of the thermoplastic sheet that is to be reversely bent to form the stacking fold.

Then, starting with the parts in the condition shown in FIG. 8 the cylinder 66 is actuated to displace movable tool part 53 upwardly half the distance d to the position shown in FIG. 9 whereby the plate wall is reversely bent to form the stacking fold indicated at 55 and having side wings 55a and 55b which are compressed together in lateral full surface engagement. Then tool part 53 is displaced back to the FIG. 8 position to release the fold 55 and facilitate removal of the now completely formed plate from the equipment.

As indicated at 60 in FIG. 9 the lateral fold forming surface of the stationary and movable tool parts may be disposed at a slight angle obliquely outwardly with respect to the axis of movement of tool part 53, for increasing the lateral force exerted on the stacking fold 55. For optimum operation including rapid and reliable removable of the formed plate the angle at 60 may be about 8 or less with respect to that axis.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. A stackable shallow container such as a plate or dish and formed from thermoplastic sheet material of uniform thickness comprising a bottom portion, a side, portion extending upwardly and outwardly from said bottom portion and a rim portion extending around the upper edge of said side portion, characterized by a continuous constant height stacking fin extending in a closed outline figure and projecting substantially axi ally downwardly from one of said portions, said fin consisting essentially of side by side continuous sections of said material in substantially full surface engagement so that the radial'spacing therebetween is less than the fin thickness and the fin thickness being substantially twice that of said material whereby whena plurality of said containers are stacked the lower end of the fin of each upper container in the stack cannot enterthe upper end of the fin in the next lower container in the stack.

2. The container defined in claim 1, wherein said 'fin comprises a closely folded wall region of said one portion, the integral lower end of said fold comprising the seating surface of said stacking fin and the upper end of said fold being a substantially seamless continuation of the upper side surface of said one portion.

3. The container defined in claim 2, wherein said fin,

is formed in the bottom portion of said container.

4, The container defined in claim 3,'wherein the bottom portion of said container is separated into a plurality of compartment defining areas, and a separate depending stacking fin is formed in each of said areas, said fins having their lower ends all disposedin a common plane normal to the container axis.

5. The container defined in claim 3, wherein said bottom portion includes a corrugated portion and said fin is formed insaid corrugated portion;

6. The'container defined in claim 3, wherein said fin 9. The container defined in claim 1, wherein said fin is a substantially cylindrical depending reversely folded wallregion around the outer periphery of said bottom portion, i

10. The container defined inclaim 3, wherein said bottom portion has a corrugated portion and said fin surrounds said corrugated portion; l 

1. A stackable shallow container such as a plate or dish and formed from thermoplastic sheet material of uniform thickness comprising a bottom portion, a side portion extending upwardly and outwardly from said bottom portion and a rim portion extending around the upper edge of said side portion, characterized by a continuous constant height stacking fin extending in a closed outline figure and projecting substantially axially downwardly from one of said portions, said fin consisting essentially of side by side continuous sections of said material in substantially full surface engagement so that the radial spacing therebetween is less than the fin thickness and the fin thickness being substantially twice that of said material whereby when a plurality of said containers are stacked the lower end of the fin of each upper container in the stack cannot enter the upper end of the fin in the next lower container in the stack.
 2. The container defined in claim 1, wherein said fin comprises a closely folded wall region of said one portion, the integral lower end of said fold comprising the seating surface of said stacking fin and the upper end of said fold being a substantially seamless continuation of the upper side surface of said one portion.
 3. The container defined in claim 2, wherein said fin is formed in the bottom portion of said container.
 4. The container defined in claim 3, wherein the bottom portion of said container is separated into a plurality of compartment defining areas, and a separate depending stacking fin is formed in each of said areas, said fins having their lower ends all disposed in a common plane normal to the container axis.
 5. The container defined in claim 3, wherein said bottom portion includes a corrugated portion and said fin is formed in said corrugated portion.
 6. The container defined in claim 3, wherein said fin is formed in an annular peripheral area of said bottom portion adjacent the lower end of said side portion.
 7. The container defined in claim 2, wherein said side portion is an inclined wall formed with a transverse ledge and said fin is formed in said ledge.
 8. The container defined in claim 2, wherein said fin is formed in said rim portion.
 9. The container defined in claim 1, wherein said fin is a substantially cylindrical depending reversely folded wall region around the outer periphery of said bottom portion.
 10. The container defined in claim 3, wherein said bottom portion has a corrugated portion and said fin surrounds said corrugated portion. 